The composition of the microbial flora of pigs, their gut innate immune function and possible susceptibility to infection is greatly influenced by the environment in which they were reared during early life (Mulder et al, 2009). Outdoor-reared pigs generally have a more developed gut immune system, perform better and are healthier than indoor-reared counterparts. The outdoor environment dramatically influences microbial diversity of the gut and is associated with high levels of Firmicutes, in particular Lactic Acid Bacteria [LAB].
LAB comprise a clade of gram-positive, low-GC, acid-tolerant, generally non-sporulating, non-respiring bacteria that are associated with certain common metabolic and physiological characteristics. LAB are rod-shaped bacilli or coccus that are characterized by an increased tolerance to a lower pH range. LAB produce lactic acid as the major metabolic end-product of carbohydrate fermentation and are amongst the most important groups of microorganisms used in the food industry.
Lactobacilli are predominant in the gut flora of organically (outdoor) reared pigs. In contrast, the numbers of these bacteria are low in indoor-reared pigs and levels of potentially pathogenic phylotypes are high (Mulder et al, 2009). Furthermore, gut immune development and function of indoor-reared pigs is known to deviate from normal. In particular, expression of Type 1 interferon genes, Major Histocompatibility Complex class I and several chemokines are known to be increased (Mulder et al, 2009).
Lactic acid bacteria may modify the flora and gut structure and function in several ways (Cotter et al, 2005; Ohashi and Ushida, 2009). For example, they may compete with harmful bacteria for key nutrients or attachment sites on the gut, resulting in their exclusion. Alternatively, they can produce bioactive substances that aid or promote colonisation by beneficial bacteria or kill/interfere with the growth of potentially harmful or pathogenic bacteria. Alternatively, these bioactive factors can be immune-modulators that promote immune development and barrier integrity of the gut. Strains of LAB vary greatly in their biological activity. The present invention seeks to provide LAB strains that have therapeutically useful properties. More specifically, the invention seeks to provide LAB strains that are capable of promoting gut and immune development and health, thereby having considerable therapeutic potential as probiotics.